Answer:
I'm going to say C.
Explanation:
This person cannot simply think a thing is so and so - he must KNOW it, which I assume means he would test it out for himself. The entire sentence indicates his mistrust of science. However, if we are just talking about the word "exact", it is in quotations and doesn't make sense with the rest of the sentence (if taken serious) so I think it is meant to be taken ironically.